JSON

json package in python can easily serialize/deserialize between json and python object.

json | python data type --- | --- [] | list {} | dict "string" | str 123.45 | int / float true/false | boolean null | None

Python data => json

json.dumps

import json

d = dict(name='Bob', age=20, score=88)
json.dumps(d)

### output ###
'{"age": 20, "score": 88, "name": "Bob"}'

json => python data

json.loads

json_str = '{"age": 20, "score": 88, "name": "Bob"}'
json.loads(json_str)

# {'age': 20, 'score': 88, 'name': 'Bob'}

json <=> python class instance

Class instance => json, we can use default in json.dumps.

• create custom function to let json.dumps use
• use __dict__ of the class instance.

import json

class Student(object):
    def __init__(self, name, age, score):
        self.name = name
        self.age = age
        self.score = score

def student2dict(std):
    return {
        'name': std.name,
        'age': std.age,
        'score': std.score
    }

s = Student('Bob', 20, 88)
print(json.dumps(s, default=student2dict))

# {"age": 20, "name": "Bob", "score": 88}

print(json.dumps(s, default=lambda obj: obj.__dict__))
# {"age": 20, "name": "Bob", "score": 88}

json => class object, we can use object_hook in json.loads

def dict2student(d):
    return Student(d['name'], d['age'], d['score'])

json_str = '{"age": 20, "score": 88, "name": "Bob"}'
print(json.loads(json_str, object_hook=dict2student))
# <__main__.Student object at 0x10cd3c190>